1. Field of the Invention
The present invention relates to cooling systems for motor vehicles powered by engines, such as trucks that are powered by internal combustion engines.
2. Description of the Prior Art
The internal combustion engine of a motor vehicle generates large quantities of heat during use. Air-cooled or liquid-cooled cooling systems remove the generated heat from the engine and other components of a motor vehicle. Air-cooling, where heat transfer occurs directly from the engine to ambient air, may be adequate for some small engines. Motor vehicles powered by large engines, however, typically require a liquid cooling system.
One such liquid cooling system uses a radiator in a coolant circuit with the engine for cooling a coolant or cooling water, and a water pump or a flow control valve to control the flow rate of the coolant that passes through the radiator. A flow control valve typically opens in response to a control signal from an electronic controller module (ECM) to circulate cooling water from the radiator with the water pump through tubing into coolant passages in the block and heads of the engine. The cooling water receives heat from the engine, then returns to the radiator. The tubing within the coolant passages can include a bypass flow passage and a heater flow passage. The bypass flow passage allows the warmed cooling water to again circulate into the coolant passages of the engine to reduce variations in water temperature and water pressure. The heater flow passage circulates the warmed cooling water between the coolant passages and a heater for warming the interior space in the cold.
In such a cooling water control system, a sensor detects the temperature of cooling water within the engine. Depending on the detected temperature, the cooling water control valve opens to control the circulation flow rate of cooling water to the radiator. This controls the temperature of the cooling water within the engine to a predetermined temperature in relation to the driving conditions, such as the engine load or engine speed, and improves the fuel efficiency, exhaust performance and drive performance of the motor vehicle. This system attempts to improve the engine power and to secure the reliability during high engine loads and may reduce friction and improve combustion during low engine load.
When the engine is required to generate a high level of driving power, the coolant temperature is lowered to increase the cooling efficiency. When the engine is required to operate with low fuel consumption, such as at a high fuel efficiency, the coolant temperature rises to increase the combustion efficiency. In this manner, the coolant temperature is controlled to achieve sufficiently high levels in opposite performances or characteristics, such as high power or output performance and low fuel consumption.
Like the engine, the transmission also heats during use. The transmission typically has a separate circuit from the transmission to the radiator for cooling the transmission fluid or oil.
Motor vehicles are used in a variety of extreme conditions. Whether driving in the blistering Arizona summer, the frigid North Dakota winter, charging up a mountain or gliding in Florida, the motor vehicle's cooling system must respond to all conditions. The cooling systems therefore are sized to meet extreme conditions, rather than normal operating conditions.
The prior art cooling systems require the entire cooling system to react to a change in conditions as it happens. Because of their size, there is a lag in cooling as these systems slowly react to these changes.
In these cooling systems control of the coolant flow, such as by the opening of the flow control valve, is based only upon a difference between the actual coolant temperature and the target coolant temperature. The cooling system thus suffers from poor response when controlling the coolant temperature to the target coolant temperature. In particular, when a quantity of heat equivalent to a cooling loss of the engine changes with a change in the operating state of the engine, coolant temperature control is poor. Here, the coolant loss is a quantity of heat removed from the engine and radiated or absorbed into the coolant in the process in which the coolant passes through the engine. If the coolant loss changes as described above, a power loss occurs which is detrimental to improvements in the fuel efficiency and the output performance. A similar problem may be encountered in a cooling system in which the flow rate of coolant passing through a radiator is controlled by an water pump, in place of the flow control valve.
Therefore, it would be advantageous to provide a cooling system that uses a smaller sized or primary system to handle cooling for most of the average road conditions, but uses an auxiliary cooling device to augment the primary system for extreme conditions. These systems could be activated manually by the driver or through the use of an electronic controller. It would also be a further advantage to provide a proactive auxiliary cooling device that could turn on and start cooling the motor vehicle before reaching extreme conditions. It would still be another advantage to have an auxiliary cooling device that could be installed optionally during assembly in a motor vehicle with modules that would react only to conditions likely to be met.